DE 10 2008 054 832 A1 discloses a laundry dryer comprising a device for cleaning a heat exchanger or process air filter arranged in a process air circuit of the dryer. Condensate generated at the heat exchanger during a drying operation of the dryer is collected in a first container from where it is fed to a liquid filter device to filter fluff from the collected liquid. The filtered liquid is collected in a second condensate container. The second container comprises a solenoid valve which is opened to convey the collected condensate by means of gravity to the heat exchanger for cleaning the heat exchanger surface, i.e. to wash off fluff.